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Erodibility characterisation for suffusion process in cohesive soil by two types of hydraulic loading / Hong Haï Nguyen in La Houille blanche, N° 6 (Décembre 2012) 

Public ISBD [article]  in La Houille blanche > N° 6 (Décembre 2012) . - pp. 54-60 Titre : Erodibility characterisation for suffusion process in cohesive soil by two types of hydraulic loading Type de document : texte imprimé Auteurs : Hong Haï Nguyen, Auteur ; Didier Marot, Auteur ; Fateh Bendahmane, Auteur Année de publication : 2013 Article en page(s) : pp. 54-60 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Geotechnical  engineering  Erosion  sensitivity  Laboratory  experiments  Suffusion  Energy  Clayey  sand Résumé : An experimental program was set up to study the suffusion process by using a triaxial erodimeter developed in our laboratory. This device is equipped with a multichannel optical sensor in order to characterize precisely the initiation and development of suffusion process. With the objective to characterize the erodibility of clayey sand, tests were performed under either flow-rate-controlled or hydraulic-gradient-controlled conditions. The test analysis allows distinguishing three steps. First, suffusion of a small quantity of clay is detected on downstream. In flow-rate-controlled conditions, this suffusion is immediately followed by a high increase of the hydraulic gradient which continues during the second step. The second step is characterized by very low amount of particles in the effluent. During the third step, high suffusion of clay appears and induces erosion of clay and sand. The results reveal the necessity to take into account the evolutions of hydraulic gradient (or pressure gradient) and also the evolutions of velocity (or flow rate) to represent the hydraulic loading. The analysis based on energy expended by fluid flow and eroded mass permits to characterize the soil sensitivity to clay suffusion and clayey sand erosion for tests under the two types of hydraulic loading. ISSN : 0018-6368 En ligne : http://www.shf-lhb.org/index.php?option=com_article&access=standard&Itemid=129&u [...] [article] Erodibility characterisation for suffusion process in cohesive soil by two types of hydraulic loading [texte imprimé] / Hong Haï Nguyen, Auteur ; Didier Marot, Auteur ; Fateh Bendahmane, Auteur . - 2013 . - pp. 54-60. Hydraulique Langues : Anglais (eng) in La Houille blanche > N° 6 (Décembre 2012) . - pp. 54-60 Mots-clés : Geotechnical  engineering  Erosion  sensitivity  Laboratory  experiments  Suffusion  Energy  Clayey  sand Résumé : An experimental program was set up to study the suffusion process by using a triaxial erodimeter developed in our laboratory. This device is equipped with a multichannel optical sensor in order to characterize precisely the initiation and development of suffusion process. With the objective to characterize the erodibility of clayey sand, tests were performed under either flow-rate-controlled or hydraulic-gradient-controlled conditions. The test analysis allows distinguishing three steps. First, suffusion of a small quantity of clay is detected on downstream. In flow-rate-controlled conditions, this suffusion is immediately followed by a high increase of the hydraulic gradient which continues during the second step. The second step is characterized by very low amount of particles in the effluent. During the third step, high suffusion of clay appears and induces erosion of clay and sand. The results reveal the necessity to take into account the evolutions of hydraulic gradient (or pressure gradient) and also the evolutions of velocity (or flow rate) to represent the hydraulic loading. The analysis based on energy expended by fluid flow and eroded mass permits to characterize the soil sensitivity to clay suffusion and clayey sand erosion for tests under the two types of hydraulic loading. ISSN : 0018-6368 En ligne : http://www.shf-lhb.org/index.php?option=com_article&access=standard&Itemid=129&u [...]

Experimental parametric study of suffusion and backward erosion / Fateh Bendahmane in Journal of geotechnical and geoenvironmental engineering, Vol. 134 N°1 (Janvier 2008) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°1 (Janvier 2008) . - pp. 57–67 Titre : Experimental parametric study of suffusion and backward erosion Type de document : texte imprimé Auteurs : Fateh Bendahmane, Auteur ; Didier Marot, Auteur ; Alain Alexis, Auteur Année de publication : 2008 Article en page(s) : pp. 57–67 Note générale : Geotechnical and geoenvironmental engineering Langues : Anglais (eng) Mots-clés : Erosion  Triaxial  stress  Cohesive  soils  Soil  structure  Hydraulic  structures Résumé : Within hydraulic earth structures (dikes, levees, or dams), internal seepage flows can generate the entrainment of the soil grains. Grain transportation affects both particle size distributions and porosity, and changes the mechanical and hydraulic characteristics of the earth’s structure. The occurrence of failures in new earth structures due to internal erosion demonstrates the urgency of improving our knowledge of these phenomena of erosion. With this intention, a new experimental device has been developed that can apply hydraulic stresses to reconstituted consolidated cohesive soils without cracks in order to characterize the erosion evolution processes that might be present. A parametric study was conducted to examine the influence of three critical parameters on clay and sand erosion mechanisms. When the hydraulic gradient was low, it was concluded that the erosion of the structure’s clay fraction was due to suffusion. When the hydraulic gradient increased, it was concluded that the sand fraction erosion initiation was due to backward erosion. The extent of the erosion was dependent on the clay content. The study underlines the complexity of confinement stress effects on both erosion phenomena. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A1%2857 [...] [article] Experimental parametric study of suffusion and backward erosion [texte imprimé] / Fateh Bendahmane, Auteur ; Didier Marot, Auteur ; Alain Alexis, Auteur . - 2008 . - pp. 57–67. Geotechnical and geoenvironmental engineering Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 134 N°1 (Janvier 2008) . - pp. 57–67 Mots-clés : Erosion  Triaxial  stress  Cohesive  soils  Soil  structure  Hydraulic  structures Résumé : Within hydraulic earth structures (dikes, levees, or dams), internal seepage flows can generate the entrainment of the soil grains. Grain transportation affects both particle size distributions and porosity, and changes the mechanical and hydraulic characteristics of the earth’s structure. The occurrence of failures in new earth structures due to internal erosion demonstrates the urgency of improving our knowledge of these phenomena of erosion. With this intention, a new experimental device has been developed that can apply hydraulic stresses to reconstituted consolidated cohesive soils without cracks in order to characterize the erosion evolution processes that might be present. A parametric study was conducted to examine the influence of three critical parameters on clay and sand erosion mechanisms. When the hydraulic gradient was low, it was concluded that the erosion of the structure’s clay fraction was due to suffusion. When the hydraulic gradient increased, it was concluded that the sand fraction erosion initiation was due to backward erosion. The extent of the erosion was dependent on the clay content. The study underlines the complexity of confinement stress effects on both erosion phenomena. En ligne : http://ascelibrary.org/doi/abs/10.1061/%28ASCE%291090-0241%282008%29134%3A1%2857 [...]

Influence of angularity of coarse fraction grains on internal erosion process / Didier Marot in La Houille blanche, N° 6 (Décembre 2012) 

Public ISBD [article]  in La Houille blanche > N° 6 (Décembre 2012) . - pp. 47-53 Titre : Influence of angularity of coarse fraction grains on internal erosion process Type de document : texte imprimé Auteurs : Didier Marot, Auteur ; Fateh Bendahmane, Auteur ; Hong Haï Nguyen, Auteur Année de publication : 2013 Article en page(s) : pp. 47-53 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Geotechnical  engineering  Suffusion  sensitivity  Laboratory  experiments  Clayey  sand Résumé : This paper deals with suffusion process also named internal instability, which takes place inside the soil skeleton. In this process, finer particles of a soil migrate within its own pore spaces. These fine particles can be cohesionless particles or clay particles. With the objective to study the effect of angularity of coarse fraction grains on suffusion a series of tests was performed on different clayey sand. Three coarse fraction type samples were tested which are different by the grain size distribution and also by the angularity of grains. A specific triaxial device was used in order to force fluid through the samples in downward direction under constant hydraulic gradients. It is shown that the angularity of coarse fraction grains may contribute to increase the erosion resistance of the tested soils by a factor of 5. Moreover for the tested soils, the grain shape has an effect on hydraulic conductivity decrease. The angularity of coarse fraction grains may intensify the geometric blocking of detached clay particles. Finally a study is conducted to compare the different ways to characterize the angularity of grains: by an analysis of grain pictures, by using an angulometer or by measuring the internal friction angle. ISSN : 0018-6368 En ligne : http://www.shf-lhb.org/index.php?option=com_article&access=standard&Itemid=129&u [...] [article] Influence of angularity of coarse fraction grains on internal erosion process [texte imprimé] / Didier Marot, Auteur ; Fateh Bendahmane, Auteur ; Hong Haï Nguyen, Auteur . - 2013 . - pp. 47-53. Hydraulique Langues : Anglais (eng) in La Houille blanche > N° 6 (Décembre 2012) . - pp. 47-53 Mots-clés : Geotechnical  engineering  Suffusion  sensitivity  Laboratory  experiments  Clayey  sand Résumé : This paper deals with suffusion process also named internal instability, which takes place inside the soil skeleton. In this process, finer particles of a soil migrate within its own pore spaces. These fine particles can be cohesionless particles or clay particles. With the objective to study the effect of angularity of coarse fraction grains on suffusion a series of tests was performed on different clayey sand. Three coarse fraction type samples were tested which are different by the grain size distribution and also by the angularity of grains. A specific triaxial device was used in order to force fluid through the samples in downward direction under constant hydraulic gradients. It is shown that the angularity of coarse fraction grains may contribute to increase the erosion resistance of the tested soils by a factor of 5. Moreover for the tested soils, the grain shape has an effect on hydraulic conductivity decrease. The angularity of coarse fraction grains may intensify the geometric blocking of detached clay particles. Finally a study is conducted to compare the different ways to characterize the angularity of grains: by an analysis of grain pictures, by using an angulometer or by measuring the internal friction angle. ISSN : 0018-6368 En ligne : http://www.shf-lhb.org/index.php?option=com_article&access=standard&Itemid=129&u [...]